Mac Pro 1.1 2006 GPU Upgrade?

You can find several cards on ebay that have been flashed and are compatible with that mac pro model. I got 4 so far for my 2 mac pro 2,1 (but compatible with 1,1 too). When selecting one, read the post. Some card have been flashed successfully and will work great on mac pro 1,1 and later, but there are some models that might have limitations due to compatibility with specific hardware on graphic cards. For instance some might have one or more port that will be non functional and usually those are specified in the item's post by the seller... some cards will not show the boot screen while others will... some will show the boot screen only if connecting a monitor on a specific port (like DVI and not on VGA or HDMI for example).

Just make sure you read well the post and select the card that best fits your needs. I've found ATI HD3870 for less than 100 dollars and HD4870 for a little below 150. Recently I came across an HD 7950 for less than $200. Usually ATI are more abundant and compatible with that model than Nvidia ones. I haven't found more recent NVidia to be available for mac pro 1,1 and 2,1 as they tend to start compatibility only with 3,1 and up.

Hope the above will help you select a card for your mac pro. Best of luck with your search and should you need further info... just post away. Cheers!